Need to build Mach3 Controller - HELP

[CNYDWW]

So i've been waiting for six months to get the rest of the money from my investor to get my prt running properly. With no date in site for the remainder of the funds and without a properly functioning cnc spring looks bleak to say the least. I'm looking into the cost of building a mach3 based controller and need some help. I can get an ebay special with a five axis board and five g540 drives within my current financial reach as a starter. What else do i need besides a power supply,case and relays. Usually when i build a computer i work from a checklist. If anyone can give me a hand setting up such a list it would be appreciated. I'd still like to run five drivers for a four axis setup. Basic wiring would also be a big help. I'm currently researching the "proper" way to set everything up.

Thank You
Regards
Randy

[Brady Watson]

Where is your ShopBot controller?

-B

[gc3]

take a look over on cnczone.....

[danhamm]

What model shopbot and what steppers do you have.? and whats up with what it came with..?

[CNYDWW]

Where is your ShopBot controller?

-B

When I bought my PRT the original controller was just a shell with the two power supplies in it. No board, no drivers and no relays. I bought the 5x10 machine for $2300 with 5hp 3phase spindle that i couldn't use and sold for $1000.

I currently have four 3.6/1 standard motors and one 7.2/1 motor i plan on using for an indexer. The machine came with all 7.2/1 motors but i did a horse trade for two of the original motors that still worked for the 3.6/1's.

The reason I ask here is simply because i trust the advice given. I'd like to see what others have done for their controller that are non shopbot. Right now the "signal generator" i'm using is only four axis, one being slave only on the x. I also can only get about 40IPM rapid transverse with it. I did find however that since it's made by flashcut inc. I may be able to get one of their DB breakoutboards and simply wire up some Geckos in a separate box with a new power supply and relay for the router.

[gc3]

do a search on g540....mach, controller upgrades.....




The G540 is limited to 50VDC, so those motors would have to be wired half-coil (black/yellow wires, red/white wires) to stay under 50VDC. Wiring the motors full-coil would require a 70VDC power supply (or something close). In other words, the torque loss from running the motors wired full-coil at 50VDC would be greater than the torque loss running the motors wired half-coil at 35VDC. To me, that is pretty good performance from a motor running on a 35VDC power supply.

Remember, that is with a 7.2:1 gear ratio and a 2,000 pulse per shaft rotation pulse requirement. Using a 3.6:1 motor (i.e. PK296A2A-SG3.6) would give you 2X the speed and the same resolution as the PRS-Alpha (7.2:1 gear ratio, but only 1,000 pulses per shaft rotation). However, the gearbox on the PK296A2A-SGxx series motor is not as robust as the gearbox on the Alpha motor, so I would be hesitant to run those PK296A2A-SGxx motors continually at high speed under heavy loads.

In any case, the limiting factor is probably the torque of the motors, not the pulse rate of the G20x board.

There are two other concerns that I have with the G540 stepper controller. The first concern is an obscure notation in the instructions. Mariss wrote: "Choose a motor that has a rated winding inductance of 2.5mH to 3mH if maximum power output (>100W mechanical) is a requirement."

Oriental Motor does not sell a geared PK296 motor that falls within the 2.5mH to 3mH range. The PK296A2A-SGxx motor is rated 1.5mH half-coil and 6mH full-coil. The PK296A1A-SGxx motor is rated 7.7mH half-coil and 30.8mH full-coil. I've posted a note on the Geckodrive forum about the 2.5mH - 3mH statement, but, so far, there has been no response.

The second concern is the use of DB25 connectors to connect the motors to the G540. At one time, I built a process control computer to replace the original electronics in the Kodak S-series photo printers. A competitor used DB-25, DB-37 and DB-50 connectors. I used much heaver duty connectors. I was often called in to trouble-shoot the competitor's electronics. Often the cause of the problem was an intermittent connection on one of the DB-xx contacts. Many DB-xx female contacts use a split (two-piece) slanted 'finger' assembly. That means that 100% of the current passing though that DB-xx contact may very easily be passing through a single contact point that is smaller than the head of a pin. That's not very much area to carry the current required by a stepper motor. If a good quality DB-25 connector is used, and if the contacts on both sides of the connector firmly mate with the contacts on the G540, then things should work properly. However, to me, that is a problem just waiting to happen. Sometime down the road, after the contact point has arced several times and carbon has built up between the two conductors, that contact point may easily become intermittent.

Even with those two concerns, if I had an extra $350 or so laying around, I would order a G540 to play with. It looks like an interesting product that could easily be connected to the G201 that Shopbot was kind enough to let me test. On the surface, it looks like the G20x from Shopbot, the G540 from Geckodrive and the PK296A2A-SGxx motors from Oriental Motor would be a good match if the motors were wired half-coil and used with a 35VDC power supply.

[garyb]

PMDX 126 breakout with 107 spindle controller the 134 gecko board and since you have the 3.6.1 motors I would go with the gecko 203's
You could add a smoother stepper as well but I'm not really a fan
Gary

[richards]

Randy,

You'll need four PK296A2A-SG3.6 or PK296A2A-SG7.2 motors wired half-coil. You'll need ONE Geckodrive G540. You'll need a 25VAC, 300VA toroid transformer, a 25A bridge rectifier (they're the same price and size as the 10A) and at least 20,000 uF capacitors (two or three caps connected parallel), various switches (disconnect, on/off, start, etc.), a contactor, and a box to put everything into.

Note that you should use the PK296A2A-SGxx, not the PK296A1A-SGxx model. The A2A model has 1.5mH inductance when wired half-coil which makes them an ideal match for a 35VDC power supply (a 25VAC transformer gives you 35VDC after the bridge rectifier and capacitors have done their job). The A1A model has 7.7mH inductance when wired half-coil, which means that you would need an 80VDC power supply. That means that you would need to use one Geckodrive G201x or G203v stepper drivers per motor and a 50VAC transformer (which would give you 70VDC).

If you use a 25-tooth pinion gear (1.25-inch pitch diameter), a motor with a 3.6:1 gearbox will move 0.000545 inches per step and the 7.2 motor/gearbox will move 0.00027 inches per step.

I've built test-bench controllers using both the G540 controller and the G203v stepper drivers (with a PMDX-122 break-out-board). With the PK296A2A-SGxx motors, either stepper driver seems to work equally well. If the G540 has all the features you need, it is much less expensive than using four G201x or G203v stepper drivers and a break-out-board.

[CNYDWW]

Thanks everyone for your suggestions. Although most of the information is over my head. I am getting help from another source that is familiar with the process. Currently i'm looking into some options with FlashCut. It's the company that produces the controller i have on the bot at the moment. The one thing i do like about Flashcut's controllers is the software. My old machine could be running in the background while i'm working on other files without issues with background processes, networking and the like. The controller itself does also run on usb. it's the connection from the controller box to the driver box that would be DB25. Once i verify the wiring i'm most likely going to purchase the parts i need from Pmdx. If i get two of their tandem motherboards five Gecko G203v's and a couple cables all i'll need is a box and power supply. I do understand the drawbacks to using the DB25 connection on the back of the controller that i do have but for the sake of my budget getting this machine up and running with acceptable performance. It may be the way to go. In the future i should still be able to use the drivers, power supply and motherboards once i can afford the rest from Shopbot. I probably wouldn't bother with the 5th driver for the fourth axis however the millwork company that i subcontract for is more interested in that then the typical work they throw my way.

Best Regards and Thanks
Randy

[HelicopterJohn]

Hi Randy,

I am just finishing up a complete electronic conversion on my Shopbot PRT 48 X 96 CNC Router. Basically, replaced everything except for the Stepper Motors.

I am in the process of putting together a video of the electronics and software that I currently use.

I used the PMDX-126 Breakout Board, 2 each PMDX 133 Motherboards, 4 each Gekco 203V drives, PMDX 107 Isolated Speed Controller coupled with the Super PID Speed Controller. I have the capability to run the software via parallel ports or USB via the Smooth Stepper. I have installed solid state relays for turning both my dust collector on/off as well as my Gast Vacuum pump. I am using an Antek 70 Volt power supply with fused circuitry. I am using the Mach3 2010 Screen Set that I have modified slightly for my use. It even has a semi-automatic tool changer macro that works like a dream. I also installed proximity switches on all the axis and have plans to possibly install a 4th axis in the future.

I just put together a general list (may have missed a couple of items) with associated prices in case anyone is interested. It is in Microsoft Word format. I have attached it for your review.

If you would like any further information just send me a PM with your e-mail and phone number and I will give you a call.

John